1. Field of Invention
The current invention relates generally to apparatus, systems and methods for amplifying a signal. More particularly, the apparatus, systems and methods relate to a power amplifier (PA). Specifically, the apparatus, systems and methods provide for a power amplifier that operates across at least an octave of bandwidth with high efficiency.
2. Description of Related Art
Amplifiers have long been used to amplify a variety of electrical signals. For example, amplifiers can be used to amplify voltage, current, power and the like. Early amplifiers used vacuum tubes to amplify signals. These tubes where large, used high power and often burned out. The invention of the silicon transistor greatly improved amplifier technology and quickly led to the extinction of vacuum tubes. Silicon transistors were much smaller, cheaper, could be more easily mass produced and had a much longer life span than vacuum tubes. Additionally, transistors consume much less power and generate less heat than vacuum tubes.
Because of a transistors small size, it has allowed for more sophisticated amplifiers to be designed. For example, operational amplifiers (Op Amps) contain two or more stages of amplification each with their own bias schemes all implemented with transistors and other discrete components. Op Amps provide excellent common mode rejection so that just a signal of interest is amplified.
Additionally prior art radio frequency (RF) amplifiers disclose various ways of doing harmonic wave shaping of voltage and current waveforms in a power amplifier to achieve high efficiency operation. Usually, these techniques use harmonic termination techniques to adjust waveforms to get the voltage and current in a proper quadrature alignment. This can provide for the maximum power output to occur at a minimum DC which provides high efficiency. Class F and inverse Class F are two of those matching modes. Historically, they have been used narrowband.
Even though there has been great progress in amplifier design, there is still need for amplifiers with enhanced efficiency, improved linearity, little to no phase change over a frequency range. Therefore, what is needed is a better radio frequency (RF) power amplifier across greater bandwidths.